Light irradiation has been utilized for various purposes such as the purpose of treating diseases such as neonatal jaundice, psoriasis, and acne, the purpose of alleviating pain, and esthetic purposes. Specifically, green light and bluish white light have been used for treatment of neonatal jaundice. Ultraviolet light has been used for treatment of psoriasis. Blue Light, red light, and yellow light have been used for treatment of acne. In this way, various types of light source have been used depending on the purposes.
For example, in the case of a light source such as an excimer lamp or an arc lamp, an affected part is placed at a certain distance from a fixed light source and irradiated with therapeutic light. However, in a case where such a lamp type of light source is used, there is concern for various types of side effect on normal sites, as the irradiation area is so large that the therapeutic light strikes other parts as well as the affected part. This makes it necessary to take some sort of shielding measure to prevent the normal sites from being irradiated with the therapeutic light, requiring time and effort for treatment. For example, in the case of treatment of a disease affecting a part of a face, a sleeping mask (blindfold) is needed to protect the eyes, which are normal sites. Furthermore, a mask designed to expose only the affected part of the face is needed to protect the normal sites of the face. Further, the patient is required to keep standing at attention for several tens of minutes while being placed under restraint for treatment. This is certainly not a good experience even for treatment purposes. Further, in the case of an affected part having a bent surface, as in the case of an arm or a leg, a lamp type of irradiation device may force the patient to take an uncomfortable posture, depending on the site such as the front side, the back side, or the lateral side. Further, irradiation intensities vary from position to position of the affected part having a bent portion, depending on the angle and distance of the affected part with respect to the lamp. This may make it difficult to uniformly irradiate the whole affected part with the therapeutic light. Furthermore, a device including such a lamp type of light source comes with many attachments such as a power source and a cooling device and, as is bulky. Such a device requires a large installation space and bears a high price. Therefore, such a device can only be installed in a facility for treatment, making it necessary to attend the facility for treatment.
Meanwhile, irradiation light from a device including a laser as a light, source forms a spotlight whose irradiation area is small. Therefore, irradiation of a large-area affected part as a whole with therapeutic light requires the spotlight to be passed over the affected part. This undesirably makes the device complex and expensive.
Further, a type of device that uses an optical fiber for planar irradiation with therapeutic light is comparatively low in efficiency in the sending of light into the optical fiber and therefore inevitably low in irradiation power. Such a device is only suited for comparatively long-term treatment.
Against this backdrop, there has been a demand for a flexible substrate including a light source that makes it possible to keep a certain distance from an affected part and cover the affected part in conformance with the shape of the affected part. In response to such a demand, several technologies such as those described below have been proposed.
For example, PTL 1 discloses a light irradiation device in which a laser and an LED are disposed as light-emitting light sources on a flexible substrate and which is wound around an affected part for use. PTL 2 discloses a facial light irradiation device in which LEDs are disposed as light-emitting light sources on a flexible substrate and which covers a face for use. PTL 3 discloses a flexible light irradiation device in which a large number of LEDs serving as light-emitting light sources are arranged on a flexible substrate and which is wound around an affected part for light irradiation. PTL 4 discloses a light irradiation device, premised on application to a head, in which an LED serving as a light-emitting light source is disposed inside a hat. PTL 5 discloses a light irradiation device in which a LED serving as a light-emitting light source is disposed on a flexible substrate and which, with a light-transmitting substance interposed between an affected part and the LED, can transmit, to the affected part, light emitted by the LED.
NPL 1 gives a description of a method for treating methicillin-resistant Staphylococcus Aureus (MRSA) infected cutaneous ulcers with near-ultraviolet light. This method of treatment is a therapy by which a part infected with antibiotic-resistant Staphylococcus Aureus is irradiated with near-ultraviolet light (at a wavelength of about 410 nm) to kill the bacteria. This method of treatment is based on a process by which systemically-administered 5-aminolevulinic acid (ALA) is metabolized and accumulated in protoporphyrin IX (hereinafter referred to as “PpIX”) in the bacteria and the bacteria are destructed from within the cells by active oxygen generated when PpIX is degraded by near-ultraviolet light. This method of treatment is a technique that has no side effects on the cells of an affected part per se and makes it possible to kill antibiotic-resistant bacteria without inducing antibiotic contamination. As such, this method of treatment has a broad range of applications and is considered to be very highly promising.
The configurations disclosed in PTLs 1 to 5 are expected to reduce various burdens such as those mentioned above on patients by covering an affected part, for example, with a flexible substrate including an LED and by irradiating the affected part with therapeutic light and to be able to uniformly irradiate even an affected part having a bent portion with therapeutic light. Further, it is conceivable that the configurations disclosed in PTLs 1 to 5 may be used to achieve the method of treatment disclosed in NPL 1.